Method of refining petroleum oil in propane solution



C. P. MCNEIL Oct. 31', 1939.

METHOD 0F REFINING PETROLEUMOIL IN PROPANE SOLUTION Filed Dec. V23, 1936 ATTORNEY QN. nimh@ indented Oct. 31, 1939 METHOD'OF REFINING PETROLEUM OIL PROPANE SOLUTION claude P. McNeil, Whiting, 1nd., mignon-4 to Standard Oil Company, Chicago, Ill., a corporation of Indiana Application December 23, 1936, Serial No. 117,288

9 Claims.

'I'his inventionv relates to refining processes employing propane, and more particularly to the refining of *hydrocarbon oils wherein the oils arev acid treated and neutralized in propane solution. l The object of the invention is to provide a system which will prevent loss of propane in the recovery system, thus not only avoiding a waste of valuable products, but preventing` the escape of propane vapors. A further object is to minimize lo the amount of caustic required in the process by employing partially spent caustic in place of fresh caustic. A further object is to avoid pumping costs and to provide a more compact and more elcient but less expensive process than has heretofore been available. The invention also contemplates further improvements in the process of propane deasphalting, acid treating and neutralizing of heavy residual lubricating oil stocks, all of which will be more clearly apparent4 from the following detailed description:

In processes wherein residual oils are fractionated by means of propane, and wherein the propane-oil solutions are `thereafter acid treated and neutralized, it has been the practice to discharge the spent caustic from the neutralization step to the sewer on the assumption that propane was relatively insoluble therein. I have discovered that this spent caustic wash which is withdrawn from the caustic settler apparently contains relatively large amounts of propane, probably in emulslfled form or dissolved in emulsied oily products. The discharge of this caustic Wash to the sewer therefore gives rise to the loss of valuable propane and at the same time it presents a dangerous' flre hazard.

Also, in prior practice it has been found that thel propane liberated in the acid sludge hydrolysis step contains acidic substances which must be eliminated from the gases before they are reu. turned to the compressor. VHeretofore it has been the practice to not only scrub thesegaseswith water but to add caustic to the scrubbing liquid ,for the neutralization of these acidic substances. I have discovered that by the extremely simple expedient of passing the spent caustic` solution from the caustic settler tothe top of the scrubber la which the acidic gases from the sludge hydroly' arefto be neutralized, I can recover valuable propane from the spent caustic wash liquid. Also,

I this spent caustic is sufficiently active toneutralize the acidic vapors and gases from the hydrolysis of the acid-s1udge. Thus I avoid the necessity of adding fresh caustic for the neutralization of acidic gases and at the same time preventpany Il loss of propane. Furthermore, I have found that the spent caustic maybe transferred from the caustic settler to this gas scrubbing system by the pressure differential' in the system and without the necessity of employing special pumps.

The invention will be more clearly understood 5` lby reference to the accompanying drawing which 'forms a part of4 the specification and in which: Fig. 1 diagrammatically represents an elevational view of my improved propane-oil rening system, and Fig. 2 is a cross section detail taken along the lo lines 2--2 of Fig. 1,

The invention will be described as applied to the treatment of' a residual Mid-Continent petroleum stock reduced by noncracklng distillation t0 a viscosity of about 400 seconds Saybolt at 210 Fn l5 It should be understood, however, that the invention is equally applicable to the treatment of any and all residual or distillate stocks as well as the treatment of synthetic oils and oil products, particularly products produced by the polymerization 20 of hydrocarbons, the condensation of hydrocarbon radicals with aromatics, products produced by oxidizing, sulfonatlng, chlorinating or otherwise chemically treating hydrocarbon oils or products,

etc. l

While the invention is described as' employing 25 propane, it should be understood that other nor-v mally gaseous hydrocarbons may be employed in lplace thereof, and the term propane is intended to include such hydrocarbons or admixtures 30 thereof with pure propane. In the preferredA example I will state conditions for a gas containing only small amountsl of butane and ethane,those skilled in the art will appreciate the necessity for slightly modifying the conditions whenI gases other than propane are used. I About 3 to 5 volumes of propane from storage tank I Il are introduced through pump Il and heater I2 to mixer I3 wherein it is intimately mixed with one volume of the Mid-Continent reo siduum from storage tank Il, steam discharge heater I5, pump I6 and line I1. 'I'he propane is preferably added to the residuum in stages I8 to avoid agglomeration of asphalt and theV entrainment of propane soluble oil therein.

is, The propane-residuum mixture is transferred through line I9 to asphalt settler 20, preferably ata temperature of F. to .120 F., or preferably about to 115 F. and-at apressure of about 250 to 400 pounds gauge, preferably about" w 390 pounds. Under these conditions the propane soluble materials separate in an -upper layer lWhich is continuously withdrawn through line II..

and pressure reduction valve!! to mixer i! wherein the solution is with gul-.

furic acid from line 24, preferably with about .1 to .4 pound of 93% acid per gallon of residuum charged. The .acid oil mixture is introduced into sludge settler 25 through a funnel-shaped device I 23 for maintaining quiescence in the settling zone,

the pressure in the sludge settler preferably being Y about 210 to 220 pounds gauge and the temperature being about 105 F.

The ,sour oil which separates from the sludge is continuously withdrawn from the settler through line 21 into mixer 23 wherein it is intimately mixed with caustic from line 29. The caustic is preferably about a 2% solution and about 0.2 gallon of caustic are introduced per gallon of sour oil (apart from propane) to be neutralized. This lis a considerable excess o`ver the amount theoretically required; an excess is necessaryto insure that satisfactory neutralization is-obtained at all times. The mixture' of sour oil and caustic is allowed to settle in caustic settler 30, the neutralized oil being withdrawn through line 3| through heater 32 to oil flash tower 33 which is provided with bubble plates 34 to prevent loss of entrained oil with propane, and which is provided with a 43 to dehydrator 4l whichV is simply a baille tower 'I'he nished oil wherein the hot oil is passed over baille plates countercurrent to air introduced through line 42. is then withdrawn through-line 43 Vto storage 44. i f l Returning to the asphalt settler, theasphalt layer is withdrawn through line 45 in amounts 1 regulated by a liquid level controlledvalve and is then passed through preheater 46 into asphalt flash tower 41. Since the asphalt flowing through the preheater tends to flow through the tubes as a solid core, I have found that ordinary exchangers are relatively ineffective but that emcient heat.

exchange can be obtained by employing concentric tubes and flowing the asphalt solution through the annular space between the tubes, the heat exchange fluid being applied either through the 1 inner tube, around the outer tube or both. By this expedient I minimize `the thickness of the layer of asphaltic material to which heat must be applied.- I have found that this expedient greatly increases the effectiveness of my.heat transfer system. I may also ux the asphalt before heating by admixing charging Astock or gas oil or both thru a branch of line 43.

Ihe flash tower is preferably maintained at a temperature of abomut 315 to 320 F. and a pressure of about 195 -pounds gauge.

Theasphat from the base of the flash tower is withdrawn through line 49 and reducing valve 53 to asphalt stripper 51|., wherein itis passed over bame plate 52 countercurrent to steam introduced Y through line753, the asphalt being withdrawn at a temperature of about 240 F. through line 54l to asphalt storagejl.'

To avoid foaming in me asphalt stripper I may introduce a spray of residuum from line 43 or a spray of lgas oil introduced through the same line.

Propane from the asphalt flash tower is with` drawn through line 56 tohigh pressure propane line 51. Propane from asphalt stripper is introduced through line 58 to line 59, thence tothe base of condenser 60 wherein it flows upwardly in the baille tower 'countercurrent to water introduced at line 6I, the condenser water being withdrawn through line 62 tofthe sewer. Propane from the top of steam condenser 60 is Atransferred through line 63 and compressor 64 to the high pressure propane line 51, thence through condenser-65 to propane storage i3. f

The acid sludge from the base of settler 25 is withdrawn through line 66..1uxed with gas oil 61 and introduced with steam from line 33 into sludge stripper or hydrolizer 69. The flux'ed rsludge flows downwardly over baille plate countercurrent to steam introduced through line 'il and the sludge leaving the systemthrough line 12 is conveyed to the acid works for the separation. 4recovery and concentration of sulfuric acid.

Propane and acidic gases from sludge stripper 69 are conveyed through line 13 to the base of neutralizing jet condenser which may be described as a scrubbing tower provided with bailles 15 into which water is introduced through line 16 and caustic is introduced through lines 11 and 18. I prefer to introduce the major portion ofthe caustic with the water since I have found that when too much of the caustic is introduced in line 18 itfmayv cause a cl gging of the system.

The caustic whic is introduced at the top of the neutralizing jet condenser is supplied through line from the base of caustic settler 33', and sinceV the caustic settler operates at about 200 pounds gauge and vthe neutralizing jet cordenser operates at about atmospheric pressure to 25 pounds gauge, it is necessary that a pressure reduction valve be employed. as indicated, although this valve may,ias in the case ofthe discharge settler, be operated by a liquid-levelicontrolled device. Thus it will De-apparent that entrained, dissolved or emulsiiied propaneI which is withdrawn from the caustic settler is not passed directly to the sewer as in prior practice, 'but is passed through lines11 and 13 to neutralizing jet condenser 14'so that the propane may be recovered from the caustic wash and at the same time the remaining alkalinity of the caustic is utilized 4for neutralizing @acidic gases from the sludge stripper. The water and spent caustic leave the neutralizing jet condenserto the sewer through line 3 I, relatively free of propane.

Propane is removed from the top of the neutralizing `iet condenser through line 13 -to line 33 and compressor 34.

Propane from oil stripper 33 is withdrawn through line 32 to line 53 and. propane from'oil flash tower 33 isi withdrawn through line 33 to line 51. Moisture-laden air from'dehydrator 4i may be vented through line 34. l

While I have described in detail a preferred embodiment of my invention, it should be underc stood that Ido not limitv myself'to any of the details hereinabove described except as defined by the following claims, which should be construed as broadly as the prior art will permit.

I claim: y .Y

` 1. The method of refining petroleum oil in propane solution which Acomprises treating said solution with sulfuric acid and separating sludge therefrom, neutralizing the acid-treated oil with aqueous caustic and separating caustic washl'm therefrom, recovering propane admixedv with acidic gases from the acid sludge and scrubbing said propane and acidic gases with the caustic wash in a closed system whereby any propane entrained in the caustic wash maybe combined with by the unspent alkalinity of the caustic in the wash may be utilized to neutralize the acidic gases admixed with the propane.

2. In a-propane deasphalting system which includes the steps of acid treating deasphalted oil,

neutralizing said acid-treated oil with aqueous caustic, stripping sludgefrom the acid treating step, and recovering' propane from said sludge and acid-treated oil, the method of conserving both caustic and propane which comprises scrubbing gases from the sludge stripping step with caustic material withdrawn from the neutralization step, and simultaneously recovering propane from the stripped sludge and from the caustic.

3. InV a propane treating system, -wherein a petroleum oil is first treated with acid and then neutralized with aqueous caustic in propane solution, and wherein an acid sludge layer and caustic wash layer respectively are withdrawn from said steps, the process oi.'` neutralizing and recovering propane from said steps which comprises countercurrently contacting the propane removed from the'acid sludge with caustic wash, whereby propaneis recovered from the wash and acidic materials from the sludge are neutralized, and

condensing and compressing the propane from the countercurrent scrubbing system for reuse in the process.

4.-A hydrocarbon-oil refining process iwhich tralized oil from the causticwash, neutralizing the propane recovered from the acid sludge with the caustic wash' and simultaneously recovering the' propane from said sludge and said caustic wash recyclingv said recovered propane for the treatment of morey oil.

5. 'I'he combination of claim 4 wherein the separated asphalt is heated inan annular zone and propane is recovered from the heated asphalt.

' 6. The method of`claim 4 wherein neutralized oil is freed from propane and dehydrated by blowing with airat a temperature of about 250` to 8. In a process ofreilning lubricating oils byl acid treatment in propane solution followed by neutralization of the sour oil with caustic wherein acid sludge is separated in the acid treated step and caustic wash is separated in` the neutralizaf tion step,rthe method of recovering propane from pane separated from the slu ge. Y

9. In a propane treating system wherein a petroleum lubricating oil stock is treated with acid in propane solution, the acidsludge is separated from the treated oil, the treated oil is neutralized with a caustic solution and a caustic wash liquid is separated from the neutralized oil, the methodl of utilizing the caustic wash liquid and avoidingy lossof propane which comprises hydrolyzing the` sludge .with open steam whereby the-heat ofv hy' drolysis supplements the heat of the steam for I distilling propane from the sludge, contacting said propane with said caustic wash liquid for removingany acidic gases that may be associated' with the propane to condense the' steam, and to recover, the propane dissolved in said caustic wash liquid, and returning the neutralized "and recovered propane for the treatment of more oil.

CLAUDE P. McNair.. 

